CVE-2026-59847: Libssh: libssh: integrity downgrade via openssl aes-gcm tag verification
A flaw was found in libssh builds using the OpenSSL backend for AES-GCM. In the decrypt path in src/libcrypto.c, the return value from EVPDecryptFinal() was checked incorrectly, so authentication tag verification failures were not handled as integrity failures. This could effectively remove integrity protection for affected AES-GCM sessions and allow an in-path attacker to modify plaintext on the wire without detection.
Other sources
A flaw was found in libssh. Incorrect AES-GCM finalization checks in builds using the OpenSSL backend can effectively remove integrity protection, allowing an in-path attacker to modify plaintext on the wire without detection.
— MITRE
Libssh: libssh: integrity downgrade via openssl aes-gcm tag verification
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 0.10.6-9
Event History
Frequently Asked Questions
What is the severity of CVE-2026-59847?
The severity of CVE-2026-59847 is rated as high with a score of 7.5.
How do I fix CVE-2026-59847?
To fix CVE-2026-59847, update libssh to a version that includes the security patch addressing the integrity downgrade issue.
What software is affected by CVE-2026-59847?
CVE-2026-59847 affects Red Hat Enterprise Linux and any products utilizing the libssh library with the OpenSSL backend.
What type of vulnerability is CVE-2026-59847?
CVE-2026-59847 is classified as an integrity downgrade vulnerability due to improper handling of authentication tag verification failures.
Is CVE-2026-59847 easy to exploit?
CVE-2026-59847 has the potential for exploitation as it affects the cryptographic integrity checks, but the impact depends on the specific implementation.